KR950012364B1 - Magnetic recording medium - Google Patents

Abstract

The media improves the running stability, drop-out protection, static electricity protection. The device includes the magnetic layer forming, the carbon black layer forming, the back coating layer which has the radius of 0.1 or 5.0 micro-meter, and 5 or 50 weight %, the relative surface area of carbon black is 200 m2/g, the compound weight of particle is 10 or 20 weight %, and the thickness of back coating layer is 0.3 or 2.0 micro-meter.

Description

Magnetic recording medium

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly, to a magnetic recording medium having improved running stability, drop-out occurrence, antistatic and the like.

In general, magnetic recording media such as magnetic tapes and magnetic disks are formed by applying a magnetic coating containing a magnetic component, a binder, carbon black and other various additives on top of a nonmagnetic support surface such as a polyester film.

In recent years, in accordance with the trend of high density recording of magnetic recording media that meets the high technological innovation of magnetic recording and reproducing apparatus, the recording signals are gradually higher in frequency, so that the magnetic recording media loses the gap with the magnetic head in the magnetic recording and reproducing apparatus. Spacing loss has a big impact on output and noise. As a countermeasure against such gap loss, it is proposed to make the magnetic layer of the magnetic recording medium as flat as possible. However, as the surface smoothness of the magnetic layer increases, a problem arises that the magnetic recording medium has poor wear resistance and deterioration in running stability.

Therefore, in order to solve such a defect, a powder of inorganic compound having high hardness such as alumina, titanium oxide, chromium oxide, calcium carbonate and the like is mixed with carbon black as the main component on the base surface opposite to the magnetic conductive layer. It is proposed to form a back coating layer dispersed and adsorbed using a vinyl chloride-vinyl oxide copolymer, a polyurethane resin, a waste glycol resin, or the like. In other words, by roughening the surface of the back coating layer to improve the running performance of the magnetic tape, and by using carbon black to obtain an antistatic effect and to suppress the adhesion of dust and dirt to reduce the drop out.

However, the magnetic recording medium having the back coating layer as described above maintains proper surface roughness and improves abrasion resistance by containing alumina, chromium oxide, or titanium oxide, but these inorganic compounds have high specific gravity and are not uniform in shape. There is a problem that this is bad. For this reason, when the medium is repeatedly used, fine separation occurs from the back coating layer, which may be an increase factor of dropout. Also, in recent years, a lot of plastics are used instead of metal materials in the manufacture of recording rolls and guide rolls of cassettes, so that the contact friction on the surface of the back coating layer is increased, so that sufficient running stability is not secured. have. It is preferable to lower the coefficient of friction in any device made of metal or plastic, but in particular, it is difficult to realize a back coating layer having a sufficiently low coefficient of friction for the guide roller made of plastic.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium which is excellent in running stability by significantly lowering the coefficient of friction in a plastic guide roll, and which does not cause a breakup, which is a rising factor of drop-out even during repeated driving.

In order to achieve the above object, in the present invention, a magnetic layer including a magnetic material is formed on one side of the nonmagnetic support, and on the other side, a nonmagnetic micropowder containing carbon black as a main component is dispersed and adsorbed with a polymer adhesive such as resin. A magnetic recording medium prepared by forming a back coating layer, wherein the back coating layer contains 5 to 50% by weight of spherical particles having a particle diameter of 0.1 to 5.0 μm, which are prepared by condensing melamine and formaldehyde, based on carbon black. A magnetic recording medium is provided.

In particular, the specific surface area of the carbon black is suitably 200 m 2 / g or less, the adsorption amount of the non-magnetic material contained in the back coating layer to the resin material is preferably 1: 2 to 3: 1 by weight ratio.

In addition, the thickness of the back coating layer made of the inert is preferably 0.3 to 2.0㎛, the addition amount of the spherical particles is preferably 10 to 20% by weight based on carbon black.

The organic condensate used in the present invention is introduced into the back coating layer instead of the inorganic compound, and is obtained by the polycondensation reaction of formaldehyde and melamine. This organic compound is easy to disperse and adsorb with resin, so it is less contaminated due to particle dropping out of the back coating layer. In particular, the coefficient of friction of the back coating layer with respect to the plastic guide roll is significantly reduced, so that the organic compound has a friction coefficient with respect to the metal guide roll. The difference is small.

Formaldehyde is highly reactive and reacts with spentol, urea and melamine to dehydrate to form a three-dimensional polymer. The organic condensate introduced in the present invention is obtained according to the following process. Specifically, melamine (I) and formaldehyde (II) react to form methyl such as trimethylolamine (III) and hexamethylolamine (IV). this will be to the methyl amine, and the amine is a condensation reaction (-H ₂ O) the organic condensation product (V) of the present invention.

The resulting organic condensate is a uniform spherical particle, an inert compound having a small specific gravity, insoluble in any solvent, and not melted by heat, and having mechanical strength capable of appropriately maintaining strength and abrasion resistance when introduced in the production of a back coating layer. If the particle size of the spherical particles is 0.1 μm or less, the surface roughness (surface roughness is preferably 0.01 to 0.03) required in the back coating layer cannot be obtained. If the particle size is 5.0 μm or more, the excessive surface roughness of the back coating layer is rather used. Since the transfer of unevenness to the magnetic layer has an effect, the electron conversion characteristics are reduced. Therefore, the size of the organic spherical particles is preferably a particle size of 0.1 to 5.0㎛.

In addition, the carbon black has a specific surface area of 200 m 2 / g or less, and when the specific surface area is too large, it is difficult to disperse the particles. This is because dropout is a significant factor.

Hereinafter, specific embodiments of the present invention will be described.

Example 1

100 parts by weight of Co-containing γ-Fe ₂ O ₃ , 20 parts by weight of a vinyl copolymer, 10 parts by weight of polyurethane, and 20 parts by weight of other additives were added with 300 parts by weight of a mixed solvent of methyl ethyl getone and toluene, and then mixed and dispersed in a sand mill. Prepare the paint. This magnetic paint is applied to one surface of the polyester film support to form a magnetic coating layer. 200 parts by weight of carbon black having a specific surface area of 200 m 2 / g or less, 60 parts by weight of vinyl chloride, vinyl acetate, vinyl alcohol, 90 parts by weight of polyurethane resin, 750 parts by weight of a mixed solvent of methyl ethyl ketone and cyclohexane, a lubricant and 5 parts by weight of the dispersant and 20 parts by weight of a white spherical body (10% by weight based on carbon black), which are organic condensates of formaldehyde and melamine, are mixed. The mixture is kneaded and dispersed to be sufficiently uniform with a sand mill, and then 20 parts by weight of polyisocyanate is added to the magnetic coating layer on the opposite side of the magnetic coating layer of the polyester film support, which is 0.3 to 2.0 μm thick. A back coating layer is formed and a magnetic tape of the magnetic recording medium according to the present invention is obtained.

Example 2

The magnetic tape of the magnetic recording medium according to the present invention was obtained by carrying out the same method as in Example 1, but adding 10 parts by weight (5% by weight based on carbon black) of the organic condensate of formaldehyde and melamine.

Example 3

The magnetic tape of the magnetic recording medium according to the present invention was obtained in the same manner as in Example 1, with the addition amount of the organic condensate of formaldehyde and melamine being 40 parts by weight (20% by weight based on carbon black).

Comparative Example 1

The magnetic tape of the magnetic recording medium was obtained in the same manner as in Example 1 except that 20 parts by weight of alumina oxide having an average particle diameter of 0.3 to 1.0 mu m was used instead of the organic condensate.

Comparative Example 2

The magnetic tape of the magnetic recording medium was obtained in the same manner as in Example 1 except that 20 parts by weight of chromium oxide having an average particle diameter of 0.3 to 1.0 µm was used instead of the organic condensate.

Table 1 shows the results of measuring the friction coefficient of the magnetic tape, the degree of contamination due to the occurrence of a drop during repeated driving, the occurrence of the dropout, the running time of the YS / N and the metal and plastic guide rolls. have.

TABLE 1

In Table 1, the friction coefficient is a ratio of the load applied to a load of 10 g by rotating the chromium plated disk at a speed of 15 rpm with the angle of winding the magnetic tape to 180 ° by sliding the back coating layer inward on a chromium plated mirror surface having a diameter of 127 mm. a T _2/10 expression μk = n is a value obtained by substituting in (T _2/10).

The degree of contamination due to breakage during repeated driving was determined by attaching the cleaning tape to the 62 mm rotating drum using the Yokohama MCS testability tester, and rotating the magnetic tape 100 times while rotating backward at 40 rpm. Was determined.

Dropout counts the number of times the reproduction output signal drops by 20 dB or more over 15 mu sec.

In addition, YS / N measured and reproduced the recording and playback using BR6400VTR manufactured by Victor Co., Ltd. in Japan, and the running time was measured by fast-forwarding and rewinding the 120-minute tape on the BR6400 VTR. Combined. At this time, the measurement was performed while changing the guide roll inside the cassette into two kinds of metal and plastic.

According to Table 1, the comparative example 1 using the conventional inorganic additives is particularly unstable in running the tape in the plastic guide roll, it can be seen that the coating film contamination occurs, resulting in a large increase in dropout.

In addition, when the chromium oxide of Comparative Example 2 was used, it could be seen that when the Y-S / N characteristic also fell by almost 1.0 dB or less due to the surface uneven transfer effect on the magnetic coating layer due to excessive grain hardness, the occurrence of contamination and dropout became more severe.

On the other hand, the magnetic tape according to each embodiment shows a good running property in the plastic guide roll, and the coating film contamination, Y-S / N, drop out occurrence characteristics are reduced.

In conclusion, in the present invention, by adding spherical particles prepared by condensing organic materials of melamine and formaldehyde to the back coating layer instead of the inorganic compound, the stability of the tape running was improved, which is higher than that of the inorganic compound. Low specific gravity, maintains spherical particles with uniform particle size, shows strong dispersibility and adsorption with fibrin resin, vinyl chloride copolymer resin, polyurethane resin, and enhances the clogging resistance. This is because there is no occurrence and the dispersibility and surface properties are improved.

In addition, when an organic condensate is used, proper surface roughness and strength can be maintained, and the problem of electronic property reduction due to the transfer of surface irregularities as a magnetic layer can be eliminated.

Claims (5)

Magnetic recording made by forming a magnetic layer containing a magnetic material on one side of the nonmagnetic support, and forming a back coating layer on which the non-magnetic micropowder mainly containing carbon black is dispersed and adsorbed with a polymer adhesive such as resin. The medium according to claim 1, wherein the back coating layer contains 5 to 50% by weight of spherical particles having a particle size of 0.1 to 5.0 µm, prepared by condensing melamine and formaldehyde, based on carbon black. The magnetic recording medium of claim 1, wherein the specific surface area of the carbon black is 200 m 2 / g or less. The magnetic recording medium according to claim 1, wherein the addition amount of the spherical particles is 10 to 20% by weight based on carbon black. The magnetic recording medium of claim 1, wherein the non-magnetic material contained in the back coating layer is adsorbed to the resin material in a weight ratio of 1: 2 to 3: 1. The magnetic recording medium according to any one of claims 1 to 4, wherein the back coating layer has a thickness of 0.3 to 2.0 mu m.